1. Field of the Invention
This invention relates to a separated core engine type turbofan engine comprising at least one core engine and at least one propulsion device, which is particularly suitable for use in a vertical take-off and landing aircraft.
2. Description of the Related Art
A conventional turbofan engine for use in a vertical take-off and landing aircraft is constituted by a fan, a compressor, a combustor, and a turbine, wherein the turbine is driven by using high temperature combustion gas as working fluid produced in the combustor, and the fan is driven by the turbine. The aircraft hovers and advances by using discharge from the fan and discharge from the turbine, and attitude control of the aircraft is performed by blowing out high pressure air which is bled from the compressor from the vicinity of the wing tip and the vicinity of the front and rear of the airframe.
A conventional example of a turbofan engine for use in a vertical take-off and landing aircraft is disclosed in Japanese Patent Publication No. H5-87655. The turbofan engine disclosed in this publication is a separated core engine type turbofan engine constituted by at least one core engine comprising a compressor, a combustor, and a turbine, and at least one propulsion device which is separated from the core engine and comprises a fan driving combustor which is supplied with high pressure air from the core engine through a high pressure air duct, a turbine, and a fan which is driven by this turbine.
The separated core engine type turbofan engine disclosed in this publication is constituted such that the core engine and propulsion device are disposed and constituted separately, and therefore the propulsion device can be disposed in a desired position without the restriction of being disposed on the same axis as the fan axis and turbine axis. When a separated core engine type turbofan engine of this type is installed in an aircraft, for example, the degree of freedom may be increased and the desired object may be achieved. In order to blow out the high pressure air bled from the compressor during attitude control of an aircraft comprising this separated core engine type turbofan engine, however, the speed of the blown out air is high. As a result, a problem arises in that a large noise is produced when the aircraft is attitude controlled. Thus in this type of separated core engine type turbofan engine, there remains scope for further improvements in relation to noise reduction during attitude control of the aircraft.
The problem that is to be solved in the separated core engine turbofan engine is therefore to reduce the speed of the air which is blown out for attitude control of the aircraft.
An object of this invention is to provide a separated core engine type turbofan engine in which noise generated during aircraft attitude control may be reduced by decreasing the speed of air which is blown out of a separated core engine type turbofan engine for the purposes of aircraft attitude control.
In order to solve the aforementioned problems, a separated core engine type turbofan engine according to this invention is constituted by at least one core engine comprising a compressor and a combustor and turbine for driving this compressor, at least one propulsion device disposed separately from the core engine and supplied with high pressure air from the core engine for driving a thrust fan, and at least one control propulsion device for controlling an aircraft and comprising an air turbine disposed separately from the core engine and driven by high pressure air supplied by the core engine, and a control fan which is driven by the air turbine.
According to the separated core engine type turbofan engine thus constituted, the turbine is driven by high temperature combustion gas produced in the combustor in at least one of the core engines, and the compressor is driven by the output of the turbine. A part of the air compressed by the compressor is transmitted to the combustor, and fuel injected into the combustor is mixed with the air and burned. The remaining part of the high pressure air compressed by the compressor of the core engine is supplied to at least one propulsion device and at least one control propulsion device which are disposed separately to the core engine. In the propulsion device, the thrust fan is driven using high pressure air supplied by the core engine, and thus thrust is obtained. In the control propulsion device, the air turbine is driven using high pressure air supplied by the core engine as working fluid, and the control fan is driven by the air turbine. The control propulsion device is provided separately to the propulsion device used for thrust in a position at which control blowout is necessary, and therefore the speed of the air necessary for aircraft control can be set at a low level such that during attitude control of the aircraft, the noise generated by air blowout for control can be reduced.
In this separated core engine type turbofan engine, the propulsion device may comprise a fan driving combustor supplied with high pressure air from the core engine, and a fan driving turbine for driving the propulsion fan. In the propulsion device, the fan driving combustor mixes the high pressure air supplied from the core engine with fuel and burns this fuel. The fan driving turbine is driven with the produced combustion gas as working fluid, and the output of the fan driving turbine drives the thrust fan such that thrust is obtained.
When a plurality of core engines is provided in this separated core engine type turbofan engine, the high pressure air from the core engines may be distributed among and supplied to at least one of the propulsion devices or at least one of the control propulsion devices via a common high pressure air control device for controlling the temperature, pressure, and so on of the high pressure air. When a system constitution comprising a plurality of core engines and a plurality of propulsion devices is provided, the temperature, pressure, flow rate, and so on of the high pressure air from the plurality of core engines are controlled by the common high pressure air control device if irregularities appear in the amounts thereof, and the high pressure air required by the respective propulsion devices and control propulsion devices is controlled by the high pressure air control device to be distributed among and supplied to at least one of the propulsion devices or at least one of the control propulsion devices.
In this separated core engine type turbofan engine, at least a part of the propulsion engines is used for vertical take-off and landing, and therefore this invention can be applied to a vertical take-off and landing aircraft. In other words, when the separated core engine type turbofan engine is applied to a vertical take-off and landing aircraft, at least one part of the propulsion devices may be used for vertical take-off and landing, and the remaining propulsion devices may be used as front and rear direction propulsion devices.